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Channel architecture consists of four major pieces: the client user interface, content management, content delivery and server components. The user interface defines the look and feel of a channel and integrates rich multimedia content into a compelling application. This application is required to deliver a variety of data types that must be displayed within the application. Content management provides the mechanism for managing and delivering scaleable multimedia. Keeping the content new and fresh requires some kind of content delivery. Push technology is the primary means for delivering new content and updates to the application. Content delivery also includes CD/DVD ROM, which provides the large storage necessary to deliver the richest possible content. All of these elements are important in the design and implementation of the channel.

The channel’s user interface is its most important component, and needs to provide an entertaining experience. Web site user interfaces are typically limited to text and graphics; for channel user interfaces, high-resolution graphics, audio, video and 3D sound can be integrated into an attention-grabbing application.

Unfortunately, performance issues related to delivering content across the Internet have been termed the "World Wide Wait," and adding 3D or interactive elements to the Internet is made difficult by the limited bandwidth available for downloading content. (For information on tools used in designing user interfaces refer to appendix B.) Distributing user interfaces stored on a CD and/or DVD-ROM can enhance the performance as well as the look and feel of a channel. Of course, the user interface requires that there be some interesting content in the first place.

Delivering rich and scaleable multimedia within a channel requires that assets be managed properly. Assets can be delivered based on bandwidth or CPU performance. Video, audio or graphic assets can reside on the Internet, local hard drive or CD-ROM. Content management ensures that the best possible video or audio is delivered to the user regardless of where it is stored. Good content management makes the retrieval of assets transparent, and the interface needs to be designed to dynamically incorporate assets of different quality.

Currently, there are a variety of content management choices. We will explore several methods using Internet browsers, link resolvers, WebCD* publisher and a database. Link resolvers can be used to redirect references on the Internet to assets residing on CD-ROM. WebCD *publisher provides a management tool for delivering Web sites on CD-ROM. Databases can be used as an alternative to manage where content resides, but also deliver content based on user preferences. The method used does not matter; the key is to manage and deliver the richest multimedia to the desktop.

Internet browsers manage assets by storing them locally in a cache. Microsoft Internet Explorer 4.0* and Netscape’s Netcaster* provide mechanisms for subscribing to channels and uses scheduled polling of the server to pull assets locally onto the user’s hard drive. The browser then fetches the Web page, graphic or asset from the cache and displays it immediately. In this way, users can browse Web sites off-line without having to access the Internet. Since the assets are stored locally, performance is greatly improved. However, the primary limitation of this method is that asset downloading is limited by bandwidth constraints, and the richness of the channel is subsequently affected.

Intel has developed a Microsoft ActiveX* control that arbitrates between assets residing on the CD-ROM, hard drive and the Internet. Assets delivered by push technology and stored on the hard drive can also be resolved using this control. The control contains parameters for specifying the name of the CD-ROM and the push directory location. The CD-ROM name is checked, and if it is not present, the user is requested to plug it in. The control then searches for the assets on the CD or hard drive before going out to the Internet. This flexibility allows the video, audio or graphic asset to be scaleable. Thus, good-quality, 30-FPS video could be stored on CD-ROM, and low-quality, 3–5 FPS video could be stored on the Internet. (Refer to the theater application in Chapter 4 for an example of how to use the Link Resolver control in your application.) A more manageable approach for converting Web sites into CDs is WebCD* Publisher.

Developers wanting to convert an existing Web site to a hybrid application should consider using a tool like WebCD publisher, which creates a deliverable CD-ROM with Web pages or assets stored locally, mixed with assets residing on the Internet. This allows developers to manage the process of creating a CD with better-quality video, audio or graphics delivered with the application.

WebCD* publisher provides an easy-to-use tool that is as simple as surfing your site and then redirecting URL links to assets residing on the CD-ROM. The tool also provides a built-in search engine and bookmarking feature for making it easier to navigate through your site. The WebCD architecture includes an ISAPI interface, which makes customization of your CD application easier. A kiosk setting allows for a branded look and feel, with the browser’s toolbars and menus eliminated.

The tool provides a comprehensive set of features to create and manage a Hybrid CD application. The game channel application was created using the WebCD* publisher, and the information in Chapter 5 covers step-by-step creation of a WebCD-based application.

A potential disadvantage of WebCD* is that the current version cannot be used to integrate Internet and CD-ROM data with data delivered by push technologies. It does, however, have a flexible ISAPI interface which could be used to extend its functionality. Push technology, meanwhile, is useful for delivering content based on user preferences, and databases provide a means to manage assets and target user preferences.

Databases on the client or the server provide an excellent mechanism for asset resolution. A client-side database can keep track of all assets that could then be queried to determine where the latest version resides. Microsoft Access, Oracle or SQL databases* provide large amounts of information that can be accessed locally or over the Internet. In the music application, Access was used to keep track of audio and video music assets that were stored on the user’s CD-ROM or hard disk. The database kept track of where the assets resided—either on CD-ROM or pushed onto the hard drive. The latest database and assets would be delivered on CD and then updated using push technology. The music application using a database to manage content is described in more detail in Chapter 4.

The advantage of using a database is that different types of assets can be mixed as well as retrieved based on user preferences. In this way, assets that are pushed or stored on CD-ROM are only presented to the user if he or she is interested in the content. A heavy-metal rock fan would probably cringe at the prospects of listening to an opera. This dual functionality makes using databases a flexible choice for developers.

The method chosen for managing multimedia assets depends on the application. Data management of assets ultimately improves the entertainment value of a channel by providing the best possible video, audio or 3D graphics integrated transparently into an easy-to-use interface. Providing better quality and scaleable assets is important for channel developers in order to ensure the success of channels.

Channels are more compelling when the best possible multimedia assets are made available to the user and there are a variety of choices for the delivery of content to a channel. Content and software can be distributed on CD/DVD-ROM, and Internet browsers incorporate smart pull to download Web sites.

The emergence of channels in Internet Explorer* and Netscape’s Netcaster* allows for the caching of Web site content onto the user’s hard drive. Both have mechanisms for subscribing to channels and scheduling downloads of information stored on Web sites. For the delivery of software or assets, push technologies such as BackWeb and Marimba provide flexible solutions. Both are capable of delivering richer multimedia content as well as content based on user preferences.

Internet applications are limited by the relatively low bandwidth of modem connections. Push or pull technology overcomes the limitation of real-time modem connections by downloading content during off hours or in the background. Medium-sized assets or software updates can be pushed, thereby keeping the application updated with the latest software and more compelling content.

CD/DVD-ROM provides a large storage medium for the delivery of rich multimedia content. High quality audio, 3D graphics and video can be delivered using either of these mediums. DVD is the ultimate storage medium, with a minimum of 4.7 gigabytes of storage. This is the equivalent of receiving more than 10 music albums on a single DVD.

In the future, the emergence of broadband will allow a variety of new and exciting applications. Higher bandwidths will facilitate the distribution of software, music and movies to the home to be stored on CD-RW and DVD-RW. With the availability of greater bandwidths, channels will no longer be limited by the size of multimedia or number of assets, enabling higher-quality video and audio to be delivered in real time to the end user.

Push technology is an essential component for delivering compelling and rich channels. Push technology can be used to overcome the limitation of real-time delivery of content over 28.8-Kbps modems. Push technology can also be used to deliver online event announcements as well as advertising, headlines and events. Users can then click on the announcement to invoke a particular channel.

Push technology is available from several companies, including Pointcast, BackWeb and Marimba*, to name just a few. These push servers allow for the delivery of assets or software updates to users after they subscribe to a particular channel. Notification mechanisms are built in that allow users to be notified of incoming updates. In addition, Internet Explorer and Netscape’s Netcaster* provide mechanisms for downloading and updating locally cached Web pages. When new information is available, new content is automatically downloaded onto the user’s local cache.

From the channel perspective, the updates are "pulled" from the client rather than "pushed" from the server. The client essentially polls the push server for new content and then downloads it if it is available. In our scenario, we are using BackWeb to push InfoPaks that contain urgent notifications for the subscriber.

Notifications alert the user to important information or updates available to the client machine. These notifications consist of small graphic files that serve as advertising banners. Other types of data that are pushed down include relatively small audio and video assets. Pushing down large audio/visual files that result in long download times is not recommended, and CD-ROM is better suited for delivery of large files.

The delivery of rich multimedia for a channel on the desktop requires that large assets be stored on CD- or DVD-ROM. Table 4-1 lists the download time required to load the storage capacity of a CD- or DVD-ROM. As you can see, it takes a lot of hours to download the same amount of data from the Internet.

CD- and DVD-ROMs can certainly be used to enhance a channel’s user interface and content. The emergence of CD-Rs opens up a new distribution mechanism for delivery of software, audio CDs and video content via push technology. CD-Rs could be used to burn downloaded albums or content onto the CD; users could purchase songs on the Internet and then burn them permanently onto a CD. Software could also be distributed and loaded onto the user’s hard disk or archived onto CD-ROM.

With the availability of DVD-ROMs, higher quality video and audio, such as MPEG2 and AC3, will become the standards for video distribution. Applications distributed on DVD will be able to deliver great-quality video without the storage limits of CD-ROM, and online distribution of movies and music will become a reality as the availability of lower cost read/writable CD- or DVD-ROMs makes possible the downloading of software, movies and music that can be permanently saved.

Eventually, the availability of 1394 Serial Bus or Firewire* will connect the PC with consumer devices such as home theaters and stereos. 1394 Serial bus provides an easy interconnect to pass digital information between these devices. DVD-ROMs or hard disks could easily be plugged in to provide supplemental storage. Hard drives could be added to cache large amounts of information distributed over broadband. Movies, music and software cached on the hard drive could then be permanently stored on a CD- or DVD-ROM. Consumers would then just record them on DVD-Rs or CD-Rs.

The availability of low-cost broadband delivery of digital channels to the PC is starting to become available to the public.

ADSL, cable and satellite broadcasts all have advantages and disadvantages relative to digital delivery to the PC. However, the consumer will eventually be able to receive digital data on the desktop at speeds of 1,000 times greater than what is currently available over a 28.8-Kbps modem. (For a better description of the benefits and limitations of broadband, refer to appendix F.)

With large pipes to the desktop, digital channels will be able to deliver much richer video, data, imaging and 3D graphics to the user in real time.

Satellite data transmission is available today in the form of DirectPC*, which gives users up to 400-Kbps download speed. Live streaming of audio or video can be combined with digital content to deliver real-time content. and rich multimedia assets such as music and video could be transmitted simultaneously to a large number of users. Users can subscribe to channels much as they tune into television broadcasts to receive new content from digital channels.

Standards for satellite and broadband delivery are emerging, and once available, channels can make use of the large bandwidth to provide new digital channels with higher quality audio and video.

So far, we have described content delivered on CD-ROM or hard drives. Another key building block of channels is the delivery of real-time information. Server technology is designed to deliver real-time content to the end user on demand.

Building a channel requires the integration of several servers. The number of servers depends on the content being delivered to the user and the business model of the channel. To be able to deliver either stored or real-time content, server solutions need to be scaleable. Channels are made more interesting with the delivery of real-time information from Web sites, streaming of real-time audio/video events and electronic commerce. The Web server is the heart of a channel, and would provide a majority of the real-time information. Electronic commerce servers provide the online stores and software necessary to purchase products from online catalogs. Real-time audio, chat and video servers provide live concerts and interviews for the channel, and push servers provide the delivery of software updates or rich multimedia over the Internet. A conceptual server configuration for a channel which supports all these data types and functionalites is shown in Figure 5-1.

Channel server software consists of the following.

· HTTP Web Server – The Web server is typically used to return Web pages or other files using HTTP. Web servers can contain scripts such as Java, CGI, Visual Basic or active server scripts to enhance Web pages.

· E-commerce Server – An e-commerce server is required to keep an online store and make online purchases.

· Database Server – E-commerce solutions typically involve databases that store customer and transaction information. Depending on the size of the database and number of users on the channel, this can be separate or integrated with the

e-commerce solution. Databases store large amounts of related information.

· Chat Server – A chat server provides real-time communities where users can meet and talk using voice or audio chat.

· Real-Time Video/Audio Server – Real-time events, such as concerts and interviews, can be delivered over the Internet.

· Push Server – A push server provides background delivery of software updates or content.

· Round Robin DNS – Round Robin DNS servers distribute millions of hits to multiple servers. This allows for scalability and support for a large amount of users.

We have covered the key elements of a channel, including user interfaces, content management, content delivery and server components. The next few chapters look at three applications: a music, a theater and a game channel. Each channel takes a different approach in the design of the major components, and the applications demonstrate the integration of technologies and concepts that go into constructing a successful channel.

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© 1997 Intel Corporation. All rights reserved.

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